The instant invention relates to the use of lutein compounds as brightening agents in thermally processed nutritional formulas.
Historically, man has used color as an indication of the safety and quality of harvested fruits, vegetables and other foods. Present day customers expect processed foods to be colored attractively and with shades that are typical of their flavor variety. The first perception of a food product is its appearance and this leads to an expectation that is compatible with that which is seen. So strong is the expectation that it is possible to over-ride subsequent sensory perceptions. In judging the quality and consistency of a product, the consumer is strongly influenced by its appearance.
The color production industry aims to meet food and drink manufacture""s needs by providing a full range of colors to suit all applications, within current legislative constraints. Consumer pressure, sociological changes and technological developments leading to more advances in the food processing industry have increased the overall color market. The most significant growth has been in naturally derived colors owing to the improvements in stabilization technologies as well as the food industry""s aim to meet the evolving consumer perception that natural is best.
Synthetic colors, natural colors, nature identical colors, and caramel colors are the primary colorants used to color foods. Currently, the permitted synthetic pigments are in the form of water-soluble dyes. Although cited as having excellent stability, soluble dyes do lose their color in certain characteristics food manufacturing circumstances. The most common problems with soluble dyes include: decolorization by ascorbic acid; loss of color resulting from microbial attack; precipitation/color loss resulting from the presence of metal ions; masking due to formation of maillard reaction products and reaction with proteins at high temperatures causing color fade.
Likewise, caramel colors also constitute a significant segment of the overall color market principally owing to their use in cola beverage drinks. They are produced by the controlled heating of carbohydrates such as sucrose, glucose and fructose. Four classes of caramels are commercially produced for specific applications. They differ in the catalyst used to promote the caramelization process.
Nature-identical colors have been developed to match their counterparts in nature. Carotenoids are one of the most common pigments that are synthesized. Carotenoids contain conjugated hydrocarbons and are therefore prone to oxidative attack and a subsequent loss of color. Color formulations containing carotenoids have been developed with antioxidant systems to reduce this effect. For most food and drink applications, the challenge to the suppliers is to provide oil and water dispersible forms of carotenoids. This is achieved using methods such as encapsulation, emulsification and pigment suspension. By using these methods, carotenoid water and oil dispersible nature-identical colors with wide-ranging pigment contents have been developed. The shade achieved with synthesized carotenoids is dependent on the formulation and processing used and varies from golden yellow to a red/orange shade.
Significant demand for natural colorants has developed over the past 25 years. The growth in use of natural colors comes from increasing consumer pressure for xe2x80x9cnaturalxe2x80x9d products. Color is spread widely throughout nature in fruit, vegetables, seeds and roots. In our daily diets, we consume large quantities of many pigments, especially anthocyanins, carotenoids and cholorophylls. Pigments from nature vary widely in their physical and chemical properties. Many are sensitive to heat, oxidation, pH change, light and their inherent solubility varies widely. With these drawbacks in mind, suppliers of natural colors have focused on the development of currently permitted pigments in three main areas: formulation technology; processing technology; and alternative sources of pigments. These approaches have proved very successful and have contributed to the increase in usage of natural colors throughout the food and drink industry.
The xanthophyll lutein is a naturally derived pigment and until recently permitted only in chicken feed in the U.S. Lutein provides color ranging from golden yellow to red/yellow. Lutein has recently been self-affirmed as GRAS (general recognized as safe) for certain food formulations, in accordance with Food and Drug Administration guidelines. Lutein is a naturally occurring oxygenated carotenoid that has no vitamin A activity. There are three asymmetric centers in lutein at C-3, C-3xe2x80x2 and C-6xe2x80x2 positions. The absolute configuration of lutein in foods is known to be 3R,3xe2x80x2R,6xe2x80x2R. Lutein is found in corn, green leafy vegetables such as spinach, kale and broccoli, and yellow-orange fruits such as peaches. Its molecular structure demonstrates its highly-conjugated carotenoid nature and its structural similarity to beta-carotene. 
Like many other carotenoids, lutein also occurs in nature as esters of fatty acids. Lutein esters are common carotenoids found in fruits such as oranges, tangerines, peaches, mangos and yellow and red peppers. Both lutein and lutein esters are fat-soluble.
In addition to the green leafy vegetables described above, lutein is found in egg yolks and in some flowers. It has been recognized as an antioxidant, which may protect against macular degeneration, a leading cause to blindness among the elderly. Commercially, it is usually extracted from the petals of the Aztec marigold. Lutein, especially when in purified form, provides a yellow to orange shade. Traditionally marigold flowers and the saponified oleoresin have been used in poultry feed to impart yellow/orange color in egg yolk. The carotenoid composition of marigold oleoresin typically contains 70% trans-lutein, 20% cis-lutein, 7% zeaxanthin, 0.58% epoxides, 1.02% unsaponifiables and 1.4% others.
Zeaxanthin, a stereoisomer of lutein, is typically found in combination with lutein and as described in Torres-Cardona et.al. below contributes a more orange color.
U.S. Pat. No. 5,997,922 to Torres-Cardona et.al. discloses the addition of 10 to 55 ppm of saponified marigold extract to poultry feed to enhance the yellow/orange pigmentation of broiler skin and egg yolk. The saponified marigold extract has a zeaxanthin content between about 20% and 80% of the total xanthophylls.
U.S. Pat. No. 3,539,686 to Rosenberg demonstrated that it is possible to obtain a wide range of tones going from yellow to red hues in broiler skin and egg yolk by using blends of xanthophylls or zeaxanthin with one or more pigments such as cantaxanthin, beta-apo-8-carotenal, ethyl ester of the beta-apo-8-carotenoic acid, and extracts from paprika and red peppers.
U.S. Pat. No. 5,382,714 to Khachik describes a process of isolating, purifying and recrystallizing substantially pure lutein apart from chemical impurities and other carotenoids for use in cancer prevention and as a safe and effective color additive for human food. The purified lutein from marigold flowers consists of 94.79% of all E-lutein, 3.03% of its geometrical isomers (Z-lutein), and a total of 2.18% of 2xe2x80x2,3xe2x80x2-anhydrolutein, zeaxanthin, alpha-cryptoxanthin and beta-cryptoxanthin.
U.S. Pat. No. 5,648,564 to Ausich et al. describes a process for forming, isolating and purifying xanthophyll crystals suitable for human consumption.
U.S. Pat. No. 6,221,417 to Sas et al. describes an in situ process for converting non-free-form xanthophylls to free xanthophylls in the biological material of the plant. The free-form xanthophylls (7.5 mg of lutein activity per kg of feed) are used to enhance the yellow color of egg yolk.
As discussed above, color is the first attribute a consumer sees of a food product. The consumer sets expectations based on their experience with the product itself, such as the yellow of egg yolks and the name given to the product, such as the creamy color with black flecks of a French vanilla ice cream. Therefore, processed foods must be colored attractively and with shades that are typical of their flavor variety. If appearance is not compatible with the expectations of the consumer, the overall appeal of the product is diminished even if the flavor is superior.
A thermally processed nutritional product""s color is the result of the colors contributed by the individual ingredients as well as the numerous ingredient interactions that occur in the final product. For example, caseinates are involved in the development of color. Amino acids react with reducing sugars in the nonenzymatic browning reaction (Maillard reaction) to produce caramel-like colors and cooked flavors. Typically, the more heat a nutritional receives during processing, the more ingredient interactions occur which often produce undesirable colors, including brown and gray. The color changes from these heat-induced reactions are illustrated in FIG. 1. The nutritional mix prior to sterilization (1A) is a bright white. However, after thermal processing in a can (1B) or glass bottle (1C) the color changes. The once white mix now presents brown and gray hues. The brown and gray colors of a vanilla flavored nutritional do not closely meet the expectations of the consumer and detract from the product""s appeal to the consumer.
Clearly, a brightening agent is required that can mask the brown and gray hues of thermally processed nutritional products. The brighter color would enhance the overall sensory acceptability of the product by the consumer.
In accordance with the present invention, it has been discovered that the addition of lutein compounds to the nutritional mix prior to thermal processing brightens the product and results in a more appealing color. Thermal processing of liquid and powder nutritionals typically impart brown and gray hues to the final color, which negatively impact the overall appeal of the nutritional. The inventors have discovered that the lutein compounds eliminate the gray and brown hues without imparting the relatively strong yellow color typically associated with lutein compounds. Additionally, the nutritionals possess long-term color stability.
Based on prior enhancement work done with lutein compounds in egg yolk, the inventors expected the supplemental lutein to add an undesirable yellow color to the vanilla, strawberry and chocolate flavored/colored nutritionals. This was further supported by statements from the supplier, Kemin Foods (Lutein a treat for the eyes, Food Processing""s Wellness Foods, August 2001), that lutein could impact color in clear or white beverages. Surprisingly, the lutein brightened the appearance of the nutritionals by masking the typical brown and gray hues of thermally processed nutritionals without the addition of a strong yellow color. This finding was unexpected in light of the use of similar levels of lutein compounds in earlier color enhancement work done in broiler skin and egg yolk, wherein the yellow/orange of the egg yolk was enhanced by the addition of 7.5 ppm to 55 ppm of lutein compounds to poultry feed.